1. Field of the Invention
The present invention relates to a thermosetting adhesive sheet to be employed for encapsulating a chip type device and, more specifically, to a thermosetting adhesive sheet to be employed for encapsulating a so-called hollow device, such as a surface acoustic wave device (SAW device), a quartz device, a high frequency device or an acceleration sensor, which is required to have a hollow surface.
2. Description of the Related Art
Conventionally, encapsulation of a chip type device such as a semiconductor element or an electronic component is achieved by a transfer molding method employing a powdery epoxy resin composition, or a potting method, a dispensing method or a printing method employing a liquid epoxy resin composition, a silicone resin or the like. These encapsulation methods require an expensive molding machine, and suffer from a problem such that the encapsulation resin adheres to unwanted portions of the device. Therefore, a less expensive and more convenient encapsulation method is demanded.
Particularly, where the conventional dispensing method employing a liquid encapsulation material is employed for the encapsulation of a device required to have a hollow surface, it is difficult to suppress intrusion of the encapsulation material into an active surface below the device. The intrusion of the encapsulation material is controlled by providing a dam on the chip or a substrate (see, for example, JP-A-2004-64732, JP-A-2004-56296 and JP-A-2005-39331). Even with this method, complete rheological control of the liquid encapsulation material is difficult. This may reduce the yield, and prevent the size reduction and the cost reduction of the device.
Thus, the conventional control of the resin encapsulation of the hollow device is not satisfactory.
In view of the foregoing, it is an object of the present invention to provide a thermosetting encapsulation adhesive sheet, which makes it possible to conveniently encapsulate a hollow device with an improved yield.